Biosludge Treatment via Steam Explosion and Pressure Release
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Solution Overview
Problem
The disposal of biosludge from pulp and paper industries poses environmental and energy efficiency challenges due to its foul smell, potential harm, high water content, and interference with processes like soda recovery, as it contains harmful substances and retains nutrients and heavy metals.
Innovation Solution
A method involving mixing biosludge with bio-based material, such as bark, and treating it at 160-295°C under pressure with steam, followed by sudden pressure release to disrupt cellular structures, making the mixture more amenable for further processing and reducing contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If biosludge is disposed of by burning, then energy is produced, but energy efficiency is low due to high water content
Solution Approach 1:
The biosludge undergoes preliminary dewatering and concentration before burning. The patent describes a process where biosludge is first dewatered in a centrifuge to remove excess water, then concentrated in a drying drum to achieve optimal moisture content for efficient combustion. This preliminary preparation eliminates the energy waste associated with evaporating water during the burning process.
2Ease of manufacture
If biosludge is mixed with black liquor for disposal, then disposal is facilitated, but process interference occurs due to NPEs
Solution Approach 1:
The patent employs a flotation process to extract and separate non-process elements (NPEs) from the biosludge before it is mixed with black liquor. Air bubbles are introduced to selectively attach to NPEs, causing them to float to the surface where they can be removed. This extraction eliminates the harmful interference that NPEs would otherwise cause in the black liquor processing system.
3Adaptability or versatility
If biosludge is disposed of in summer when combined heat and power boilers have downtime, then alternative disposal methods are needed, but disposal options are limited
Solution Approach 1:
The patent transforms the biosludge through physical and chemical parameter changes to create a versatile product suitable for multiple disposal pathways. The biosludge is dewatered, concentrated, and optionally chemically treated to modify its properties. This produces a stabilized material that can be disposed of through multiple methods including landfarming, composting, or storage, allowing the system to adapt to seasonal boiler availability changes.
4Loss of energy
If biosludge is burned after mixing with fibrous primary sludge, then disposal is achieved, but energy efficiency remains compromised
Solution Approach 1:
The patent implements preliminary dewatering and concentration of both biosludge and fibrous primary sludge before mixing and burning. The process involves passing both streams through centrifuges and drying drums to achieve optimal moisture content prior to combustion. This preliminary water removal ensures that the subsequent burning process operates at high energy efficiency, eliminating the need to evaporate large amounts of water during combustion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method significantly reduces contaminants, increases energy content, and allows for efficient disposal and utilization of biosludge, producing a product suitable for energy production with lower ash and odor, and can be implemented continuously.
Implementation Method 1
treating the mixture at a temperature in the range of 160 - 295°C under pressure in the presence of steam; and releasing the pressure suddenly or explosively to disrupt the structure of the mixture
Data Source
Figure 1
AI summary
(57) Abstract The invention relates to a method for the treatment of biosludge, wherein the method comprises mixing biosludge with a bio-based material to form a mixture, wherein the dry matter of the biosludge is at least 0.01 % (w/w) of the total dry matter of the mixture; treating the mixture at a temperature in the range of 60 -295°C under pressure in the pres- ence of steam; and releasing the pres- sure. (Fig. 1)